The present invention relates to a method and apparatus for forming gold plating by performing photodeposition.
Gold plating has satisfactory anti-corrosion and superior electrical characteristics. Thus, gold plating is often applied to electrodes or contacts of electronic components. The gold plating is formed by performing electroplating or electroless plating. When performing electroplating, the object that is plated functions as a cathode. Thus, the plating object must be conductive. Accordingly, the plating object is a conductive body made of a conductive metal or an insulative body coated with a conductive film.
Compared to electroplating, electroless plating (chemical plating) is more advantageous in that electric current is not required to flow through the plated object when plating the object.
There have been experiments in which light was irradiated when plating metal (I. Zouari, F. Lapocque, M. Calvo, and M. Cabrera: J. Electrochem. Soc. 139 (1992) p. 2163). However, the light was used to mainly generate heat and increase the deposition rate.
When performing electroless plating, the parameters of metal deposition are the type of metal compound, the oxidation reduction potential of a reductant in a plating liquid, and the rate of reaction between the metal compound and the reductant. The parameters are changed to control the deposition of metal when immersing the object that is to be plated in the plating liquid. When locally plating an object, the object must be locally masked.
It is an object of the present invention to provide a method for easily forming gold plating on an object regardless of whether or not the plated object is made of a conductive material and regardless of whether or an object must be plated locally or entirely. It is another object of the present invention to provide an inexpensive apparatus for forming gold plating.
One aspect of the present invention is a method for forming gold plating on an object. The method includes preparing a solution containing gold ions and a reductant, immersing the object that is to be plated in the solution, irradiating the object with ultraviolet rays, and depositing gold on the object to form gold plating when the ultraviolet rays cause a photochemical reaction in the solution.
Another aspect of the present invention is a method for forming gold plating on an object. The method includes preparing a solution containing purified water, tetrachloroauric acid for providing gold ions, sodium sulfite serving as a reductant, and diluted sulfuric acid for adjusting the pH value of the solution. The method further includes immersing the object that is to be plated in the solution, irradiating the object with ultraviolet rays, and depositing gold on the object to form gold plating when the ultraviolet rays cause a photochemical reaction in the solution.
A further aspect of the present invention is an apparatus for forming gold plating on an object. The apparatus includes a tank for accommodating a solution containing gold ions. A support is arranged in the tank for immersing the object that is to be plated in the solution. A light source irradiates ultraviolet rays toward the object.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.